This invention is concerned with a sealing device for shafts of food processing machines, such as shafts bearing augers, rotary cutters, and the like, in machines such as cheese processing machines, bread kneading machines, mincers and mixers for sausage processing, etc.
In machines of the kind listed above, shafts bearing members such as augers, cutters and the like are driven by motor means external to the processing area, and enter the processing chamber through a bore in the chamber wall, with a sealing gasket preventing the processed matter from leaking out of the chamber. Such gaskets are a critical point in the machine, because they have unusual requirements. On the one hand, it is necessary to lubricate the gasket for a good mechanical operation, but, on the other hand, it is unacceptable to use a conventional lubricant such as oil or grease in an area which is in direct contact with food. Moreover, it often happens that fluid components of the food penetrate the interface between the gasket lip and the shaft and build dregs favoring bacterial growths, which will subsequently contaminate the inside of the processing chamber. Even the cleaning to which the machine is subjected at the end of a work session will not remove such dregs, because of the very sealing action yielded by the gasket itself: therefore, for an effective and thorough cleaning, the shafts have to be removed from their journals, with waste of time and work; moreover, disassembling a shaft is a delicate mechanical operation, requiring skill in the subsequent reassembly.
In summary, gaskets of operating shafts in food processing machines are a highly critical aspect of the machine, and in practice it has been necessary heretofore to use compromises between mechanical and sanitary requirements.